To build a text string that can be displayed or extruded, etc. you need to define a "String" parameter. Use Tools->Parameters and "String" is one of the drop-down entries for the "Type". Let's assume its name is "txtmrk".
Now you build the string using the values, using Tools->Relations.
--- [ Begin Relations ] ---
numdigits = 1
txtmrk = ""
IF D5 < 1.0
txtmrk = txtmrk + "0."
ELSE
txtmrk = txtmrk + ITOS ( floor ( D5 ) ) + "."
ENDIF
txtmrk = txtmrk + EXTRACT ( ITOS ( floor ( 10^numdigits * ( 1 + D5 - floor ( D5 ) ) ) ), 2, 1 )
txtmrk = txtmrk + "x"
IF D6 < 1.0
txtmrk = txtmrk + "0."
ELSE
txtmrk = txtmrk + ITOS ( floor ( D6 ) ) + "."
ENDIF
txtmrk = txtmrk + EXTRACT ( ITOS ( floor ( 10^numdigits * ( 1 + D6 - floor ( D6 ) ) ) ), 2, 1 )
txtmrk = txtmrk + "x"
IF D7 < 1.0
txtmrk = txtmrk + "0."
ELSE
txtmrk = txtmrk + ITOS ( floor ( D7 ) ) + "."
ENDIF
txtmrk = txtmrk + EXTRACT ( ITOS ( floor ( 10^numdigits * ( 1 + D7 - floor ( D7 ) ) ) ), 2, 1 )
--- [ End Relations ] ---
Now that you've got the parameter that contains the text you need. Whenever you define a text entity in a sketch, you can tell it to "Use Parameter" and pick the "txtmrk" you defined in the relations.